The state House gave preliminary approval Wednesday to allowing Sierra Vista, Benson and other cities to ignore the requirements that developers must prove they have an assured 100-year supply of water.

The Central Arizona Project is one of the largest water projects in the country, delivering nearly 60 percent of Arizona’s share of Colorado River water to cities, farms, industries and Native American tribes in central and southern Arizona.

Republicans say they're not satisfied with a U.S. Environmental Protection Agency claim that a 3-million-gallon toxic spill from an inactive gold mine was likely "inevitable," even though there had been prior warnings that such a spill could occur.

Citing the release of millions of gallons of toxic wastewater into a southwestern Colorado river earlier this month, a coalition of conservation groups, two Arizona Native American tribes and two county governments petitioned federal agencies Tuesday to tighten mining regulation on public lands.

Authorities say rivers tainted by last week's massive spill from an abandoned Colorado gold mine are starting to recover, but for the Environmental Protection Agency the political fallout from the disaster could linger.

Arizona officials continue to monitor a massive spill of toxic sludge that is heading toward the Colorado River, but most were hopeful Tuesday that it will have little impact by time it reaches the state.

Drawing groundwater from near a stream can suck that stream dry. In turn, using all the water in streams and rivers lessens their ability to replenish the aquifers beneath them. Yet California and Arizona -- the two states water experts say are facing the most severe water crises -- continue to count and regulate groundwater and surface water as if they were entirely separate.